
^ F»ft f- 











CONTRIBUTIONS FROM THE LABORATORY OF TIIE UNIVER¬ 
SITY OF PENNSYLVANIA. 

i 



By F. A. Genth. 

n 


{Bead before the American Philosophical Society , August 21s£, 1874.) 


On several occasions I have given descriptions and analyses of tellurium 
minerals, which have been found associated with the gold ores of this 
country. Since my last paper on this subject (Amer. Journ. of Science 
[2] NLV., 30G-319) several highly interesting discoveries have been 
made, which not only augment the list of species, but also corroborate 
some of my former observations. 

Most important is the occurrence of the tellurium ores at the Red 
Cloud Mine, near Goldhill, in Boulder County, Colorado. Prof. B. Sil- 
liman (Journ. of Science [3] VIII. 25-33), has given a very accurate and 
careful description of some of the minerals found at this locality, and 
an exceedingly interesting account of the get logical position of the vein. 

Through the liberality of my friend J. F. L. Scliirmer, Esq., Super¬ 
intendent of the United States Mint at Denver, Colorado, I have been 
put in possession of a considerable quantity of very pure aDd excellent 
material for investigation, including several varieties not mentioned by 
Prof. Silliman. 

Another interesting locality of tellurium minerals is the Briggs or 
King’s Mountain Gold Mine, sometimes called the Gaston Mine, in Gaston 
Co., N. C., where I noted this occurrence about two years ago. 

A third one is in the neighborhood of Highland, Montana. Several 
others of minor importance will be mentioned under the different species. 

The following are the results of my investigations : 








2 


1. Native Tellurium. 

The occurrence at the Red Cloud Mine is fully described by Prof. Sil- 
liman. I have observed it on several specimens in small, very indistinct 
crystals, with rounded edges; also in one splendid cleavage piece, shovr- 
a plate of § of an inch in length, and nearly 4 of an inch in width, from 
which I have obtained a hexagonal cleavage crystal of of an inch in 
length, and { of an inch in thickness. Generally it is disseminated in 
line grains through quartz, cleavage perfect, color tin-white, inclining to 
gray. 

Associated with sylvanite, altaite and pyrite. 

Without destroying my best specimens, I could not get enough of pure 
material for analysis. 


2. Tetradymite. 

The sulphurous variety of tetradymite has been observed at several 
new localities : associated with gold ores in small lead-colored scales at 
Spaulding Co., Georgia ; also in York District, S. C. ; in quartz from the 
gravel deposits of Burke and McDowell Counties, N. C. ; in gray quartz 
with gold at the Montgomery Mine, Hassayampa District, Arizona ; and 
at the “Uncle Sam’s- Lode,” in Highland District, Montana. At the 
latter place it is found associated both with quartz and gold, and in 
dolomite. Part of it is oxydized into montanite. The latter, however, 
is not in a state of sufficient purity for analysis. That the tellurium is 
pretent as telluric acid, and not as tellurous acid, is proved by the large 
evolution of chlorine, when it is heated with chlorhydric acid.* 

The tetradymite occurs here in considerable quantity, in foliated 
masses with folke sometimes f of an inch in width and scaly-granular. 
Its color is between lead-gray and iron-black. It is often tarnished with 
pavonine colors. 

The gold, wli.icli is often interlaminated with it, shows the striation of 
the tetradymite, and is evidently the result of its precipitating action 
upon the gold in solution, in the same manner as already stated in my 
notice of the pseudomorplious gold after tetradymite from the White 
Hall Mine (Amer. Journ. of Science [2] XNVI1I., 254). 

It is an interesting fact that the tetradymite from Uncle Sam’s Lode 
contains sulphur as an essential constituent, while that from the gold 
placers of Highland, wdiich I had received from Mr. Kleinsclimidt, and 
described in the Journal of Science [2] XLV., 316, is free from it. 

My friend Mr. P. Knabe has made some very important observations 
on this subject, which are contained in his letter, dated Highland, Mon- 

* I notice the following misprints in Dr. Burkart’s paper, “ Tiber das Yorkommen 
verschiedener Tellur-Minerale in den Yereinigten Staaten von iNord-Amerika,” Leon¬ 
hard & G-einitz Neues Jahrbuch der Mineralogie, etc., 1873. page 491. line51rom bottom : 
Tellursceure instead of Tellurige Secure, and on page 49‘2, line 15, Tellurige Secure in¬ 
stead of Tellursceure. 


3 


tana, Dec. 20th, 1870, of which I translate that part which refers to this 
subject. He says : 

I have discovered the tetradymite which I sent you in Uncle Sam’s 
Lode, in Highland District. Two years ago I examined a fragment of 
tetradymite from Highland Gulch , which I found to be the sulphurous 
variety , and was therefore very much surprised to find from your pamphlet 
that the tetradymite from Highland Gulch examined by you was the variety 
without sulphur. After I had repeatedly examined pieces of the said 
mineral, I made the discovery that both varieties of tetradymite are found 
together in Highland Gulch. This was the more interesting, since there 
occur in it also two different varieties of gold, which fact gives pretty con¬ 
clusive evidence that the gold of the Gulch comes f rom two different forma¬ 
tions. The finest gold of the Gulch originates undoubtedly from the garnet 
which occurs between the dolomite and granite. I then examined the differ¬ 
ent trial pits in the dolomite , and found in this formation at the head of the 
Gulch in the Uncle Sam Lode the specimens which I sent you. In the 
garnet rock which adjoins the Gulch on its left side, I have not yet found 
any tetradymite ; but in a piece of garnet from the Gulch I found gold and 
tetradymite without sulphur. In all the samples of the sulphurous variety 
of tetradymite from the Gulch , as well as in that from Uncle Sam’s Lode, 
I found a trace of selenium.” 

The following are the results of my analyses of the tetradymite from 


Uncle Sam’s Lode : 

Broadly foliated. 

Smaller scales from 



dolomite. 

Sp. Gr. = 

7.332 

— 7.542 

Quartz — 

0.05 

— 0.58 

Gold = 

0.21 

— - 

Bismuth = 

00.49 

— 59.24 

Copper - - 

trace 

— 0.47 

Iron = 

0.09 

— - 

Telllurium (by diff.) = 

34.90 — 

(by diff.) 34.41 

Selenium = 

trace 

— 0.14 

Sulphur = 

4.26 

— 15.16 


100.00 

100.00 


At the Red Cloud Mine, Colorado, tetradymite seems to be one of the 
rarest minerals. The first indication which I had of it was the observa¬ 
tion of a small quantity of bismuth in the analysis of one of the varieties 
of petzite. After a great deal of search I discovered, associated with 
pyrite and auiiferous hessite, a very few minute iron-gray scales, some 
of them with a bluish tarnUh, which on examination proved to be the 
sulphurous variety of tetradymite. 

3. Altaite. 

I have discovered this rare mineral at two new localities—the Red 
Cloud Mine, Colorado, and the King’s Mountain Mine, Gaston Co., N. C. 






4 


At tlie latter locality it is found in sugary quartz associated with gold, 
galenite, chalcopyrite, pyrite, antimonial tet railed rite, and more rarely 
with nagyagite and a greenish micaceous mineral resembling fuehsite. 
It occurs in small quantities only, and is so much mixed with the other 
minerals, that I was unable to select enough for a quantitative analysis. 
It is easily recognized by its tin-white color, with the greenish-yellow 
hue, and its great lustre. It is found in particles showing the distinct 
cubical cleavage, but also finely granular. A very interesting but quite 
small piece shows a cleavage mass, part o p which is altaite, part galenite, 
without any interruption in the cleavage plane, both minerals being 
easily distinguishable by their color. 

The altaite at the Red Cloud Mine, Colorado, is found in larger masses, 
generally, however, very much intermixed with other minerals, espe- 
cially native tellurium and sylvanite. It is associated with pyrite, siderite 
and quartz. Sometimes it is found in indistinct cubical crystals, appar¬ 
ently coated with a thin film of galenite ; rarely in larger cleavage masses. 
I have a cleavage cube of § of an inch in size of distinct cleavage : some 
of the planes are slightly coated with galenite. The most frequent occur¬ 
rence is that in granular masses with indistinct cubical cleavage, a frac¬ 
ture inclining to subconchoidal and a yellowish tarnish.* 

The analysis of a portion of the cleavage cube gave the following 
results : 


Spec. Gr. 

— - 

8.060 



Quartz 


0.19 

—• 

0.32 

Gold 

— 

0.19 

— 

0.16 

Silver 

— - 

0.62 

— 

0.79 

Copper 

= 

0.06 

— 

0.06 

Lead 

— 

60.22 

— 

60.53 

Zinc 

— 

0.15 

— 

0.04 

Iron 

— - 

0.48 

— 

0 33 

Tellurium 


37.99 

— 

37.51 



99.90 


99.74 


4. IIessite, Auriferous Hessite, Petzite. 

Varieties of telluride of silver with variable quantities of gold are the 
principal minerals which give the ores of the Red Cloud Mine their value. 
1 believe that I was the first to whom specimens of the rich auriferous 
variety were sent by Mr. Scbirmer. These I have determined as petzite. 
Prof. Silliman mentions a variety (1. c.) containing 7.131 per cent, of gold 
and 51.061 per cent, of silver, of which he gives a very accurate descrip¬ 
tion ; he evidently had only this one , and therefore comes to the conclu¬ 
sion that the Red Cloud Mine contained no other varieties. It will be 

* In l)r. Burkart’s paper (1. c.) p.487, line 12 from tlie bottom, read: hexaedrische 
Instead of hexatjonalc . 




o 


seen from the analyses which I give below, that there are several, from 
almost pure hessite without gold, up to the highly auriferous of the same 
composition as that from the Stanislaus and Golden Rule Mines in Cali¬ 
fornia. 

a. Hessite. 

The pure hessite appears to he very rare. I have received only one 
small piece, which Mr. Schirmer distinguished as “black tellurium.” 
It is of a dark iron-gray color, inclining to black, granular structure and 
uneven fracture ; pow der dark lead-gray ; sectile. Its spec. gr. = 8.178. 

It contains some cavities lined with minute crystals of pyrite and 
barite. 

The analyses gave : 


Gold 

= 

0.22 

— 

0.20 

Silver 

zzz: 

59.91 

— 

60.19 

Copper 

= 

0.17 

— 

0.16 

Lead 

• — 

0.45 

— 

0.18 

Zinc 

— 

trace 

— 

trace 

Iron 

— 

1.35 

— 

1.20 

Tellurium 

— 

37.86 

by diff. — 

38.07 



99.96 

% 

100.00 


In all the other varieties, the difference in the appearance of the 
mineral is so slight that it is almost impossible to distinguish them. 
They all have an iron-gray color, and frequently assume by tarnishing a 
darker or purplish color, a subconchoidal fracture; the more argentiferous 
are somewhat darker, the more auriferous lighter and more brittle. 


b. Auriferous IIessites. 



a 

Sp. gr. = 8.789. 


gr. : 

Quartz 


0.18 — 

0.13 

— 0.70 

Gold 

— 

3.31 — 

3.34 

— 13.09 

Silver 


59 68 — 

59.83 

— 50.56 

Copper 

— 

0.05 — 

0.06 

— 0.07 

Lead 

— 

- — 


0.17 

Zinc 

— 

- — 


— 0.15 

Iron 

~ : 

0.15 — 

0.21 

— 0.H6 

Tellurium 


1 

o 

o 

G 

36.74 

— 34.91 



100.97 — 

100.31 

100.01 



c. Petzite. 





a 


ft 

Sp. Gr. 


9.010 

— 

9.020 

Quartz 

— 

0.62 

— 

0.05 

Gold 

. — 

24.10 

— 

24.69 

Silver 


40.73 

• — 

40.80 











6 


Copper 


trace 

— 

trace 

Bismuth 

— 

0.41 

— 


Lead 

—- 

0.2G 

— 

— 

Zinc 

—• 

0.05 

— 

0.21 

Iron 

— 

0.78 

— 

1.28 

Tellurium 

— 

33.49 

by diff. 

32.97 



100.44 


100.00 


The above analyses, to which add for comparison those of Prof. Silli- 
mau and the petzite from Nagy-Ag, give the following atomic ratios 
between gold, silver and tellurium : 


b a = 

1 

32.7 

• 

O' 

34.3 

Silliman = 

1 

14 


— 

b/S 

1 

7 


8.2 

Nagy-Ag = 

1 

4.7 


5.9 

Petzite — 

1 

i*' 1 , 


4.2 


From which it will he seen that gold and silver appear to replace each 
other in indefinite proportions, while the mixture of the two combines 
atom for atom with tellurium. 

5. Sylvan ite. 

The Ited Cloud Mine is the first American locality at which this mineral 
has been found. It was observed by Prof. Silliman, but his stock was 
not sufficient for a more minute description. The specimens which I 
have are massive, showing eminent cleavage in one direction, giving it a 
plated appearance. In one piece it occurs in quartz, which is penetrated 
by crystalline aggregations arranged in a line of over one inch in length 
and g 1 ^ of an inch in thickness, resembling the real “graphic tellurium ” 
from Transylvania. Its color is silver-white, with a strong gray tint ; 
brilliant metallic lustre. 

It is associated with pyrite, which, in very small crystals, is often so 
thickly disseminated through the mass, that it is very difficult, if not 
impossible, to obtain pure material for analysis. 


Quartz 


Sp. gr. — 7.943. 

a ft r 

0.32 — 0.86 — 0.59 

Gold 

— 

24.83 — 

23.06 — 25.67 

Silver 

— 

13.05 — 

11.52 — 11.92 

Copper 

— 

0.23 — 

0.57 — 0.21 

Lead 

= 

- — 

- — 0.46 

Zinc 

— 

0.45 — 

0.11 — 0.06 

Iron 

— 

3.28 — 

4 84 — 1.17 

Tellurium 

— 

56.31 — 

54.60—by diff.—58.87 

Selenium 

— 

trace — 

trace — trace 

Sulphur 

— 

1.82—by diff. 

= 4.44 — 1.05 



100.29 

100.00 100.00 












The atomic ratios between gold, silver and tellurium, and the com¬ 
bined gold and silver and tellurium are as follows : 

« Au : Ag : Te = 1 : 0.96 : 6.98 — (Au Ag) ■: Te = 1 : 6.6 

P “ : “ : “ = 1 : 0.91 : 7.29-- “ : “ =1 : 3.8 

Y “ : “ : “ — 1 : 0.84 : 6.45— “ : “ =1 : 3.5 

6. Calaverite. 

I have observed one very minute specimen of this rare mineral amongst 
those from the lied Cloud Mine, which Mr. Schirmer sent me. It fully 
answers the description which I have previously given (1. c.). 

It is associated with sylvanite and quartz. It contains a somewhat 
smaller percentage of silver than that from the Stanislaus Mine in Cali¬ 
fornia. 

The scarcity of tlie material did not allow me to obtain for analysis 
more than 0.1654 grs., from which 0.0050 grs. of quartz were deducted. 
Dr. G. A. Koenig reduced 0.0332 grs. before the blowpipe, and obtained 
42.32 per cent, of gold and silver, which I then separated with tlie results 
given below. 


It contains : 



Gold — 

40.59 — 

39.76; 

Silver = 

2.24 — 

2.56 

Tellurium — 

57.67 — bydiff. 

— 57.68 

Copper and iron = 

traces 



100.50 

100.00 


I was in the hope that I would find in the oxydized specimens of the 
tellurium ores from the Red Cloud Mine interesting products of decom¬ 
position, but observed hardly anything else than native gold, sometimes 
in very minute scales in the partly decomposed petzite, and small quali¬ 
ties of cerargyrite. There is also a minute quantity of what is probably 
tellurate of silver present, because if the oxydized minerals be treated 
with ammonic hydrate, and the amnionic solution be filtered and boiled, 
and subsequently acidulated with nitric acid, the argentic chloride be 
precipitated, the filtrate from this contains both silver and tellurium. 

I also observed among the oxydized pieces, one which had a yellowish 
coating, probably montanite ; the quantity, however, was too small for 
any investigation other than a determination of the presence of bismuth 
and tellurium. 

7. Tellurate of Copper and Lead—a new mineral. 

This new tellurate has been discovered by Mr. P. Knabe, in the “Iron 
Rod” Mine, Silver Star District, Montana. He had sent me a small 
quantity of the same, which consisted of an apparently uniform siskin- 
green powder. 






8 


\ * 

I had intended to make a full investigation of the same, but unfortu¬ 
nately it has been mislaid or lost. 

However, I will give the most important part of the information about 
its occurrence, which I have received in Mr. Knabe’s letter, dated High¬ 
land, March 20th, 1871. 

“Isend you enclosed a mineral from the Iron Rod Mine, Silver Star 
District, Montana, which I hope will be interesting to you. The same sub¬ 
stance apparently is found in the Silver Star District in all the veins which 
occur in the crystalline states. I have not examined that from the Iron 
Rod Mine, because I did not want to use up a portion of the already small 
quantity—but in a mineral of exactly the same appearance from the ‘ ‘Green 
Campbell ” Mine, in the same District, I have found oxides of copper and 
lead and telluric acid. I shall try to obtain it from different mines in 
order to ascertain whether it is constant in its composition or is a mixture. 
In the Green Campbell Mine it is found as a thin coating upon the selvage 
of the footwall, whilst in the Iron Rod Mine it occurs in the fissures of the 
rock. ’ ’ 

In the same letter Mr. Kuabe mentions the interesting fact of having 
examined a graphite from the Harvey Lode, occurring in the dolomite, 
which contains 2.1 per cent, of silver. 

This is the last information which I have received from Mr. Iv.; in it 
he states that iu the latter part of May, 1871, he would make explora¬ 
tions in the.wilderness, 40 miles W. of Highland. 

8. Bismutiiinite. 

Dr. Burkart states in an appendix to his observations (1. c.) on the 
American Tellurium Minerals, (Leonhard & Geinitz Neues Jahrbuch, 
etc., 1874, 9,) that in the Las Animas Mine on the Sugar Loaf Mountain, 
Colorado, bismuth ores are found—either native, or in combination with 
sulphur and tellurium. 

The few small pieces of bismuth ores which I have seen from this lo¬ 
cality were bismutliinice. in stout columnar aggregations, in great part 
converted into bismutliite, but with still a large percentage of undecom¬ 
posed tersulpliide. 

It contained a small percentage of silver, but not a trace of tellurium. 

9. SCHTRMERITE—A NEW MINERAL. 

Massive, finely granular, disseminated through quartz ; no cleavage 
could be observed ; fracture uneven ; soft, brittle. Sp. G. = 0.737 ; lead- 
gray inclining to iron-black, lustre metallic B. B. fuses very easily 
and gives the reactions of bismuth, lead, silver and sulphur. 

After deducting LOO per cent, quartz in analysis I., and 1.07 per cent* 
in II., the results are as follows : 


9 



I. 

II. 

Lead 

— 12.69 

12.76 

Silver 

= 22.82 

24.75 

Bismuth 

= 46.91 by diff. 

47.27 

Zinc 

= 0.08 

0.13 

Iron 

= 0.03 

0.07 

Sulphur 

= 14.41 

15.02 


96.94 

100.00 

The atomic ratios of Pb : Ag : Bi : S are very nearly 

= 1:4: 

corresponding with the composition : PbS, 2 Ag 2 S, 2 Bi 2 

S 3 , which 

Pb 

= 11.71 


Ag 

== 24.45 


Bi 

= 47.54 


S 

= 16.30 



100.00 

It is allied to and closely resembles cosalite. 
Dedicated to J. F. L. Schirmer, Esq. 


P./S. Since the reading of my paper an article has appeared in the En¬ 
gineering and Mining Journal, of August 29th, 1874, on “ Tellurium 
Ores of Colorado, by Fred. M. Endlich,” which I must not pass unno¬ 
ticed, as it contains several statements which I cannot endorse. 

The paper shows that Dr. Endlich had not a sufficient quantity of pure 
material for his examinations, and therefore based his new species upon 
a partial examination of mixtures. 

His “ Schirmerite ” is evidently nothing else but a mixture of petzite, 
either with pyrifce or perhaps with a telluride of iron—a mineral which 
has not yet been found in its pure state, the existence of which, however, 
is probable from the fact that both, the true and the auriferous hessites, 
which are quite free from sulphur, invariably contain a minute quantity 
of iron—which according to my analyses varies from 0.15 to 1.35 per 
cent. 

If Dr. Endlich had given his name to a good species, I would very 
cheerfully have adopted it and given another to my new sulphbismuthide 
of silver and lead—but as the mixture which he describes is not entitled 
to a name, that of “ Schirmerite ” must remain for my species. 

His “ Henryite” is undoubtedly nothing but an altaite, with an admix¬ 
ture of pyrite. 

Knowing from Mr. Schirmer, that he has given me for this investiga¬ 
tion the purest and best of all the minerals, which have occurred at the 
Ked Cloud Mine, I can state without hesitation that Dr. Endlich’s spe¬ 
cies have no existence. 


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